Histology

Question 1

What are the 4 major type of cells found in the Epidermis

Answer 1

Keratinocytes
 Melanocytes
 Intraepidermal macrophages
 Tactile epithelial cells

Question 2

Mutation of keratin 5 and 14 is the cause of what disease

Answer 2

Epidermolysis bullosa simplex

Question 3

Mutation of karatin 1 and 10 is the cause of…

Answer 3

Epidermolytic hyperkeratosis

Question 4

Defects of keratin 2e cause…

Answer 4

ichthyosis bullosa of siemens

Question 5

Defects of keratin 09 is associated with…

Answer 5

Epidermolytic palmoplanter keratoderma

Question 6

Cacitriol hormonal actions

Answer 6

Increases calcium absorption from the gut
Increases calcium reabsorption from the kidney
Increases bone mineralisation
Vitamin D receptor binding apoptosis

Question 7

Function of MITF
Lack of MITF leads to what disorder
Excess of MITF leads to what disorder

Answer 7

Functions to regulate melanocyte differentiation
.Albinism
.Melanoma

Question 8

Mutation in the gene for tyrosinase leads to what?

Answer 8

leads to less melanin
leading to albinism

Question 9

What is Vitiligo

Answer 9

• Autoimmune loss of melanocytes - white patches on
  otherwise normal skin
• Largely a cosmetic issue
• Some individuals pursue complete depigmentation of skin to
  generate a uniform skin colour

Question 10

function of unencapsulated nerve endings

Answer 10

Mediate PAIN, TEMPERATURE, non-discriminative touch(Crude touch (or non-discriminative touch) is a sensory modality that allows the subject to sense that something has touched them, without being able to localize where they were touched (contrasting “fine touch”).)

Question 11

Functions of Apical Dark cells inMerocrine sweat glands

Answer 11

Secrete glycoproteins by exocytosis(merocrine secretion)

Question 12

Function of Basal clear cells

Answer 12

Secrete water and electrolytes into the intercellular canaliculi

Question 13

What type of a genetic disorder is cystic fibrosis and in what gene does the mutation occur leading to disorder

Answer 13

Genetic autosomal recessive disorder - Mutation in the CFTR gene (Cystic
Fibrosis Transmembrane conductance Regulator), affects epithelial
transport of Cl

Question 14

Compare and Contrast Na+ and Cl- transport in normal sweat duct and Na+ and Cl- transport in sweat duct of CF sufferer

Answer 14

Na+ and Cl- transport in normal sweat duct

As primary sweat moves along the duct most of
the NaCl is reabsorbed.
* This is driven by a large inward gradient for Na+,
which flows into the cell through epithelial Na+
channels (ENaC) in the apical membrane.
* This Na is then transported out of the cell and
into the blood via the basolateral sodium pump
(Na+/K+ ATPase).
* Because Cl- is electrically attracted to Na+, it
follows it by flowing through the CFTR Clchannels
* The result is the production of dilute sweat, so
that we can be cooled by evaporation without
losing an undue amount of salt.

Na+ and Cl- transport in sweat duct of CF sufferer
* In CF sweat ducts, Cl- conductance is
completely abolished because of
defective CFTR.
* When Na+ attempts to flow out of a CF
duct through remaining sodiumselective pathways, it is unaccompanied
by Cl-.
* This creates an excess of negative
charge in the duct which attracts Na+
and prevents its further absorption.
* Therefore very little NaCl is
reabsorbed, resulting in a high salt
content (>100 mM vs. typical values of
20-30 mM in healthy individuals) in CF
sweat.
* The sweat chloride concentration is
the most reliable single physiological
marker of CF.

Question 15

What are the functions of the skin

Answer 15

Thermoregulation, Protection (mechanical and against microorganisms), Water barrier, Cutaneous sensations, Excretion and absorption, Synthesis of Vitamin D.

Question 16

What are the three major layers of the skin

Answer 16

Epidermis, Dermis, Subcutaneous (hypodermis) layer.

Question 17

Describe the structure of the epidermis

Answer 17

Comprised of multiple layers of cells, including keratinocytes, melanocytes, intraepidermal macrophages (Langerhans cells), and tactile epithelial cells.

Question 18

What is the main function of keratinocytes?

Answer 18

Keratinocytes protect the skin and underlying tissues from abrasions and heat, contribute to wound healing, and produce a water-repellent sealant to reduce water loss and protect against foreign materials.

Question 19

How do keratinocytes mature through the epidermis, and how is the epidermal permeability barrier formed?

Answer 19

Keratinocytes mature from the basal layer to the superficial layer over a 3-4 week period, undergoing characteristic changes and filling with keratin. The epidermal permeability barrier is formed through the production of multi-lamellar lipids, cornified cell envelope, and the keratin-filaggrin complex.

Question 20

hat are the types of junctions between skin cells, and what are their functions?

Answer 20

Tight junctions, adherens junctions, desmosomes, and hemidesmosomes. They contribute to cell-cell communication, adhesion, and stability, forming barriers and anchoring points.

Question 21

How is Vitamin D3 produced, and why is it important?

Answer 21

Vitamin D3 is synthesized in the skin through UV exposure, essential for normal absorption of calcium and phosphorus from the intestine, and crucial for various physiological functions including immune function.

Question 22

Explain the process of melanin synthesis by melanocytes.

Answer 22

Melanocytes produce melanin, which protects the skin from UV damage. The synthesis pathway involves the conversion of phenylalanine to tyrosine, oxidation of tyrosine to DOPA, and further reactions leading to the production of either eumelanin or pheomelanin.

Question 23

How do Langerhans cells contribute to immunity in the skin?

Answer 23

Langerhans cells, also known as intraepidermal macrophages, recognize and present antigens to the immune system, perform phagocytosis, and play roles in allergy and chronic skin inflammation.

Question 24

What are the different types of sensory receptors in the skin, and what do they detect?

Answer 24

Merkel receptors, Meissner corpuscles, Ruffini cylinders, Pacinian corpuscles, and free nerve endings. They detect pressure, touch, vibration, and temperature changes.

Question 25

Explain the pathophysiology of cystic fibrosis and its impact on sweat production.

Answer 25

Cystic fibrosis is caused by a mutation in the CFTR gene, resulting in the production of thick secretions that can obstruct various organs. In sweat ducts, defective CFTR channels lead to impaired chloride transport, resulting in high salt content in sweat.